imgact_binmisc: abstract away the list lock (NFC)
This module handles relatively few execs (initial qemu-user-static, then qemu-user-static handles exec'ing itself for binaries it's already running), but all execs pay the price of at least taking the relatively expensive sx/slock to check for a match when this module is loaded. Future work will almost certainly swap this out for another lock, perhaps an rmslock. The RLOCK/WLOCK phrasing was chosen based on what the callers are really wanting, rather than using the verbiage typically appropriate for an sx. MFC after: 1 week
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@ -98,6 +98,16 @@ static int interp_list_entry_count;
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static struct sx interp_list_sx;
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#define INTERP_LIST_WLOCK() sx_xlock(&interp_list_sx)
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#define INTERP_LIST_RLOCK() sx_slock(&interp_list_sx)
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#define INTERP_LIST_WUNLOCK() sx_xunlock(&interp_list_sx)
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#define INTERP_LIST_RUNLOCK() sx_sunlock(&interp_list_sx)
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#define INTERP_LIST_LOCK_INIT() sx_init(&interp_list_sx, KMOD_NAME)
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#define INTERP_LIST_LOCK_DESTROY() sx_destroy(&interp_list_sx)
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#define INTERP_LIST_ASSERT_LOCKED() sx_assert(&interp_list_sx, SA_LOCKED)
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/*
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* Populate the entry with the information about the interpreter.
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*/
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@ -198,7 +208,7 @@ imgact_binmisc_find_entry(char *name)
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{
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imgact_binmisc_entry_t *ibe;
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sx_assert(&interp_list_sx, SA_LOCKED);
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INTERP_LIST_ASSERT_LOCKED();
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SLIST_FOREACH(ibe, &interpreter_list, link) {
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if (strncmp(name, ibe->ibe_name, IBE_NAME_MAX) == 0)
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@ -256,9 +266,9 @@ imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
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}
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}
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sx_xlock(&interp_list_sx);
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INTERP_LIST_WLOCK();
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if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) {
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (EEXIST);
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}
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@ -267,7 +277,7 @@ imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
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SLIST_INSERT_HEAD(&interpreter_list, ibe, link);
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interp_list_entry_count++;
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (0);
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}
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@ -281,14 +291,14 @@ imgact_binmisc_remove_entry(char *name)
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{
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imgact_binmisc_entry_t *ibe;
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sx_xlock(&interp_list_sx);
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INTERP_LIST_WLOCK();
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if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (ENOENT);
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}
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SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, link);
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interp_list_entry_count--;
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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imgact_binmisc_destroy_entry(ibe);
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@ -304,14 +314,14 @@ imgact_binmisc_disable_entry(char *name)
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{
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imgact_binmisc_entry_t *ibe;
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sx_xlock(&interp_list_sx);
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INTERP_LIST_WLOCK();
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if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (ENOENT);
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}
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ibe->ibe_flags &= ~IBF_ENABLED;
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (0);
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}
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@ -325,14 +335,14 @@ imgact_binmisc_enable_entry(char *name)
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{
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imgact_binmisc_entry_t *ibe;
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sx_xlock(&interp_list_sx);
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INTERP_LIST_WLOCK();
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if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (ENOENT);
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}
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ibe->ibe_flags |= IBF_ENABLED;
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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return (0);
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}
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@ -343,8 +353,7 @@ imgact_binmisc_populate_xbe(ximgact_binmisc_entry_t *xbe,
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{
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uint32_t i;
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sx_assert(&interp_list_sx, SA_LOCKED);
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INTERP_LIST_ASSERT_LOCKED();
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memset(xbe, 0, sizeof(*xbe));
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strlcpy(xbe->xbe_name, ibe->ibe_name, IBE_NAME_MAX);
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@ -375,14 +384,14 @@ imgact_binmisc_lookup_entry(char *name, ximgact_binmisc_entry_t *xbe)
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imgact_binmisc_entry_t *ibe;
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int error = 0;
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sx_slock(&interp_list_sx);
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INTERP_LIST_RLOCK();
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if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
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sx_sunlock(&interp_list_sx);
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INTERP_LIST_RUNLOCK();
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return (ENOENT);
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}
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error = imgact_binmisc_populate_xbe(xbe, ibe);
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sx_sunlock(&interp_list_sx);
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INTERP_LIST_RUNLOCK();
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return (error);
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}
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@ -397,7 +406,7 @@ imgact_binmisc_get_all_entries(struct sysctl_req *req)
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imgact_binmisc_entry_t *ibe;
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int error = 0, count;
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sx_slock(&interp_list_sx);
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INTERP_LIST_RLOCK();
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count = interp_list_entry_count;
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xbe = malloc(sizeof(*xbe) * count, M_BINMISC, M_WAITOK|M_ZERO);
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@ -407,7 +416,7 @@ imgact_binmisc_get_all_entries(struct sysctl_req *req)
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if (error)
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break;
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}
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sx_sunlock(&interp_list_sx);
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INTERP_LIST_RUNLOCK();
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if (!error)
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error = SYSCTL_OUT(req, xbe, sizeof(*xbe) * count);
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@ -546,7 +555,7 @@ imgact_binmisc_find_interpreter(const char *image_header)
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int i;
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size_t sz;
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sx_assert(&interp_list_sx, SA_LOCKED);
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INTERP_LIST_ASSERT_LOCKED();
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SLIST_FOREACH(ibe, &interpreter_list, link) {
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if (!(IBF_ENABLED & ibe->ibe_flags))
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@ -584,7 +593,7 @@ imgact_binmisc_exec(struct image_params *imgp)
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sname = NULL;
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/* Do we have an interpreter for the given image header? */
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sx_slock(&interp_list_sx);
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INTERP_LIST_RLOCK();
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if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) {
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error = -1;
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goto done;
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@ -702,7 +711,7 @@ imgact_binmisc_exec(struct image_params *imgp)
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imgp->interpreter_name = imgp->args->begin_argv;
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done:
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sx_sunlock(&interp_list_sx);
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INTERP_LIST_RUNLOCK();
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if (sname)
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sbuf_delete(sname);
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return (error);
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@ -712,7 +721,7 @@ static void
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imgact_binmisc_init(void *arg)
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{
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sx_init(&interp_list_sx, KMOD_NAME);
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INTERP_LIST_LOCK_INIT();
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}
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static void
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@ -721,15 +730,15 @@ imgact_binmisc_fini(void *arg)
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imgact_binmisc_entry_t *ibe, *ibe_tmp;
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/* Free all the interpreters. */
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sx_xlock(&interp_list_sx);
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INTERP_LIST_WLOCK();
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SLIST_FOREACH_SAFE(ibe, &interpreter_list, link, ibe_tmp) {
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SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry,
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link);
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imgact_binmisc_destroy_entry(ibe);
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}
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sx_xunlock(&interp_list_sx);
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INTERP_LIST_WUNLOCK();
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sx_destroy(&interp_list_sx);
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INTERP_LIST_LOCK_DESTROY();
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}
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SYSINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_init,
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